Inovance MDBUN-60-5T - Working Principle and Load Curves

Inovance MDBUN Series Braking Unit User Manual
Page 5 of 24
2.3 Working Principle of the MDBUN
Figure 2-2 Application principle of the MDBUN braking unit
Status
indication
Braking
control board
Operation
panel
interface
DI1
DO1
DO2
DC
+
P(+)
BR
External
braking
resistor
Block diagram of
the braking unit
Connect the common bus
terminal + of the drive
Connect the common bus
terminal – of the drive
DC
Voltage
detection
Auxiliary
power supply
Braking
IGBT
–
The braking unit consumes the electric energy fed back from the motor to the drive to limit
the voltage of the drive within a secure range.
Before normal running of the braking unit, you need to set the braking start and stop
voltages based on the AC power voltage class of the drive. The following figure shows the
braking start and stop voltages and voltage during normal running of the main capacitor.
Figure 2-3 Working principle of the MDBUN braking unit
Acceleration or
stable-speed
running
Braking running at
deceleration
Stop Start
Braking running at
deceleration
Stop
(P0-00)
(P0-01)
(P0-02)
Bus voltage (V)
Braking start
voltage
Braking stop
voltage
Normal bus voltage
Braking
IGBT state
Braking unit
DO output
Time (s)
As shown in the preceding figure, the relationship between three voltages is as follows:
Braking start voltage > Braking stop voltage> Normal bus voltage. When the braking unit
is in the master mode, the control circuit detects the bus voltage in real time. If the bus
voltage reaches the set braking start voltage (set in P0-00), the braking IGBT starts to
work and discharges the electricity in the main capacitor of the drive through the external
braking resistor, so that the bus voltage reduces to lower than the braking stop voltage
(set in P0-01). The start braking rate (set in P0-02) of the braking unit can also be set to
adjust the discharge rate during braking so as to change the braking time.